There is described in applicant's patent application, Ser. No. 07/513,599, filed Apr. 24, 1990, entitled Pipeline Repair Method and Apparatus, which is incorporated herein in its entirety by this reference, an apparatus for boring a hole in the wall of a pressurized plastic gas pipe and inserting through the opening a stopper having a deformable, resilient skin so as to block the flow of gas in the pipe while the pipe is being repaired. An insertion assembly for inserting the stopper into the pipe is the subject of a divisional application of the above referenced application, Ser. No. 07/605,988, filed Oct. 29, 1990. As taught in the above referenced Patent Applications, the stopper is inserted into the pipe by means of a gate valve assembly which serves to provide a pressurized space for the insertion and removal of the stopper, thereby preventing the escape of gas from the pressurized pipe during the stopper insertion and removal operation. Thus, each time that the stopper is to be inserted into the pipe so as to block it, the gate valve assembly must be used along with the stopper insertion assembly, and the same is also true each time it is desired to withdraw the stopper from the gas pipe.
A gate valve, of necessity, is a relatively bulky piece of equipment, and it would be desirable if its use were not required each time a deformable stopper is to be inserted into or withdrawn from the gas pipe. Further, it would be desirable if apparatus which is used to actuate the stopper could be left in place with the stopper, but could be readily removed for inspection and repair or replacement at any time, without gas escaping from the pressurized gas pipe.